We are pleased to offer you our ULTIMATE Dynaco ST-70 upgrade kit, the Dyna-70.
We have developed this kit to bring your tired old ST-70 power amp up to modern tube amp standards with many improvements over the original Dynaco driver circuits.
This is indeed a RADICAL upgrade to your ST-70, really changing how this amp operates and sounds.
We assume that all the transformers in your existing ST-70 are in working order.
Speaking of transformers, do take note of this VERY IMPORTANT point with regards to the PA 060 power transformer.
Dynaco had two types of PA 060 power transformers they used. The PA 060 transformer used in the very early kits had a very low 'stack' about 1"/25.4mm high. Then Dynaco came out with a transformer with a notably higher stack, about 1 3/4"/44.5mm high. This is the size transformer we are using in our test ST-70 and we've had NO issues with using this size. Yes, it gets warm, but this is quite normal!
Do also note, that since with our kit the 5AR4 rectifier tube is no longer used, the 5VAC secondary winding is also no longer used which will lessen the overall load on the PA 060 keeping its running temperature lower!
We cannot guarantee that the very early 1"/25.4mm stack height PA 060 power transformer will be able to comfortably handle the extra filament current used by the 6SN7 driver tubes!
You can of course upgrade the PA 060 by buying one from one of the many suppliers, this is even larger again with a 2"/51mm stack height and with this model PA 060 you could even use the KT88 family of tubes.
We recommend that you stick with the EL34 family of power tubes,  as all our testing etc. was done using the EL34.
The cricuit is based on the classic Mullard design of the 50's with certain improvements to bring it up to 'modern' tube circuits, including an LM334 based constant current source for stable performance.
The bias adjusting circuit includes a safety resistor, which will prevent the bias and hence the power tube from going into orbit should a bias trimmer fail.
The  kit comes complete with ALL parts, including hardware and wires. You will need to splice some of the wires, as the original length on some wires are too short, for that, we supply colored wires and heat shrink for the joints! We also supply a 3 way power cord where the chassis will be grounded to your house ground. This is an important safety upgrade!
The full details are all covered in the comprehensive instruction manual you will get with the kit.
The coupling capacitors supplied with the standard kit are the excellent SOLEN or DAYTON AUDIO film capacitors.
As an option, you can buy the excellent sounding Russian PIO (Paper In Oil) coupling capacitors.
Other options available are new three way speaker posts, GROUND, 4 OHM & 8 OHM and new RCA sockets.
We have made no compromises with the quality of the componets used for this kit.

- Nichicon, United Chemi-Con and other name brand electrolytic capacitors
- 1% high grade film resistors in the signal circuits
- Panasonic Metal Oxide resistors for the power supply
- Solen coupling capacitors, (Russian PIO capacitors as an option)
- top quality FR4-TG standard black printed circuit board, 0.08"/2mm thick, with dual ground planes for ultimate screening

Also to note is that with our kit, the STEREO/MONO switch will no longer work/is disabled and the two front octal sockets are converted to measure the bias level for each output tube.
This kit is not complicated, but your are working with extremely high voltages, in excess of 720VAC & 400VDC, so EXTREME care MUST be taken! These voltages can be LETHAL!
We also stress that good soldering skills are a must have, this can make all the difference for a trouble free project. We strongly recommend that you use a temperature controlled soldering iron, such as a Weller or HAKKO, with small as well as medium sized tips. 98% of all issues our clients have with building a kit is related to bad soldering, so AGAIN we stress, good soldering skills are a MUST!!



The Ultimate Dynaco ST-70 Upgrade Kit

Please note: ALL our kits require assembly!
Also, all parts are mixed together, they are not packed in their individual values and/or types.
Price for the complete kit with Solen coupling capacitors: $155.00 plus $15.00, which will be added when you check out. Shipping cost is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs.
Tubes ARE NOT included, see below for tubes.


Price for a quad set of matched Tung Sol EL34 power tubes:
$107.00, plus $12.00 shipping which will be added when you check out.
Shipping cost is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs.
If you buy these tubes together with the kit, shipping will be refunded
Price for a trio of matched Tung Sol 6SN7 triodes:
$82.00, plus $12.00 shipping which will be added when you check out.
Shipping cost is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs.
If you buy these tubes together with the kit, shipping will be refunded

Price for a set of Russian PIO coupling capacitors, consisting of 4x 0.22uF 400 or 500V & 2x 0.1uF 400 or 500V:
$20.00 plus $8.00 shipping which will be added when you check out. NOTE: These PIO's are ONLY sold in conjunction with the Dyna-70 kit and NOT for general purchase, thank you.
Shipping cost is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs.
If you buy these capacitors together with the kit, shipping will be refunded

Dyna-70

supplied components may vary from photos
a typical completed Dyna-70 upgrade using the optional Russian PIO coupling capacitors
Tubes are not included!

pcb with the standard French made Solen coupling capacitors
pcb with the optional Russian PIO coupling capacitors
We also offer to do the upgrade for you. You ship us your old ST-70 and any tubes you want to be used and we carry out the conversion with our Dyna-70 kit.
We assume that all the transformers on your ST-70 are in working order and within specs. If we find any issues with any of the parts, we will contact you and go from there.
The conversion time is 2 weeks from receipt of your ST-70. We will also warranty the kit for a period of 6 months. This is for the kit only, we do not warranty any other parts.
If you also choose to buy new tubes from us, these too will have a 6 month warranty. This warranty starts the day the ST-70 arrives back at your home.
Please pack your ST-70 carefully. Remove all tubes and pack separately, use a double walled corrugated shipping box and really make sure the amp cannot move inside the box. We of course cannot and will not take any responsibilities for the shipping to us.
When we ship the amp back to you, we will insure in, we recommend you do the same when you send it to us!

The cost for us to install our Dyna-70 kit into your ST-70 is $300.00, this is ON TOP of the kit price and any tubes or other parts you decide to order as well, plus shipping back to you.
We require full payment up front, this is not negotiable
Shipping will be charged separately once your amp is packed up and ready to go.




To finish off your Dyna-70 upgraded ST-70, why not add this slick front panel to it!
It is made from anodized aluminum with engraved lettering finished with black lacquer. This will really give your ST-70 that custom look!
The panel is supplied with all the hardware consisting of two RCA jacks with pcb, machine screws and six test jack sockets for bias measurement.

Cost for this panel and the parts is US$82.25 plus $15.00 shipping to the lower 48. For all other areas and countries, please contact us for additional shipping costs. If you buy this panel together with the kit, shipping will be refunded.

NOTE: We do not keep these panels in stock, they will be ordered when we get your order. It will take 10 working days to have this panel made and then shipped out to you!
Price for a new set of 3 way speaker posts on a new pcb to replace the old unit.
This is for a pair of speaker posts:
$13.50 plus $8.00 shipping which will be added when you check out.
Shipping cost is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs.
If you buy these speaker posts together with the kit, shipping will be refunded

Price for a set of RCA jacks complete with pcb to replace those old worn out units:
$15.00 plus $8.00 shipping which will be added when you check out.
Shipping cost is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs.
If you buy these RCA jacks together with the kit, shipping will be refunded


Price for a new power switch to replace the old worn out unit:
$5.00.
The free shipping is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs.

NOTE: the above price is ONLY valid when purchased with the Dyna-70 kit!



Price for a quad set of matched Electro Harmonix 6CA7 'big bottle' power tubes as an alternative to the EL34:
$118.00, plus $12.00 shipping which will be added when you check out.
Shipping cost is for the lower 48 only! For all other areas and countries, please contact us for additional shipping costs.
If you buy these tubes together with the kit, shipping will be refunded
For the Auto Bias version of this kit, Dyna-70AB, click here.